Ajin OVA is not so important to watch if you're reading the manga, especially if we talk about the second episode.. Episode 1 - Another tragic story about being an Ajin.. Nakamura Shinya has something in common with Nagai Kei, still being interesting.. even if it were something we saw already - Episode 2 - A funny episode with our characters, something simple at first.. but impressive at the end - Episode 3 - Satou's past, huh?.. Some of the things we saw in the manga already.. like the first episode.. it was exaggerated, very.. some people are disappointed of this.. but I liked it, hey guys, COMEON.. It's Satou-San!!!!.. everything about my bae will be great, doesn't matter if it follows the manga or not.